Global Error Handling In Javascript
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undefined function error thrown. Is there a global error handling facility in Javascript? The use case is catching function calls from flash that are not defined. javascript javascript-events share|improve this question asked Jun 4 '09 at 16:53 Bob What do you want to do with an error once you catch it? Do you just need to log it so you can create the missing function, or are you looking to exception handling in javascript example stop exceptions from breaking your code? –Dan Herbert Jun 4 '09 at 17:00 2 I would like to get the name of the missing function called and based on presence of some string call my own function. Any call to a function with the string 'close' would call my close() for example. I would also like to trap the error at that point. –Bob Jun 4 '09 at 17:06 1 exceptionsjs.com provides this functionality and can be taylored to only catch errors related to undefined functionality with its "guard" functionality. –Steven Wexler Aug 4 '14 at 2:48 add a comment| 9 Answers 9 active oldest votes up vote 126 down vote accepted Does this help you: I'm not sure how it handles Flash errors though... Update: it doesn't work in Opera, but I'm hacking Dragonfly right now to see what it gets. Suggestion about hacking Dragonfly came from this question: http://stackoverflow.com/questions/645840/mimic-window-onerror-in-opera-using-javascript share|improve this answer edited Jun 4 '09 at 17:04 answered Jun 4 '09 at 16:57 Ionuț G. Stan 98.2k14141171 3 With the addition of msg, file_loc, line_no params this should do it for me. Thanks! –Bob Jun 4 '09 at 17:16 1 I have just released code to
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80kFollowers JavaScript Article A Guide to Proper Error Handling in JavaScript By Camilo Reyes April 13, 2016 window.onerror script error This article was peer reviewed by Tim Severien and Moritz Kröger. Thanks to all of SitePoint's peer reviewers for making SitePoint content the best it can be! http://stackoverflow.com/questions/951791/javascript-global-error-handling Ah, the perils of error handling in JavaScript. If you believe Murphyʼs law, anything that can go wrong, will go wrong! In this article I would like to explore error handling in JavaScript. I will cover pitfalls and good practices. We'll finish by looking at asynchronous code and Ajax. More from this author Saved from https://www.sitepoint.com/proper-error-handling-javascript/ Callback HellQuick Tip: How to Throttle Scroll EventsGetting Started with the Raspberry Pi GPIO Pins in Node.js I feel JavaScriptʼs event-driven paradigm adds richness to the language. I like to imagine the browser as this event-driven machine, and errors are no different. When an error occurs, an event gets thrown at some point. In theory, one could argue errors are simple events in JavaScript. If this sounds foreign to you, buckle up as you are in for quite a ride. For this article, I will focus only on client-side JavaScript. This write up will build on concepts explained in the article Exceptional Exception Handling in JavaScript. To paraphrase: “with an exception JavaScript checks for exception handling up the call stack.” I recommend reading up on the basics if you are not familiar. My goal is to explore beyond the bare necessities for handling exceptions. The next time you see a nice try...catch block, it will make you think twice. The Demo The demo we
a fair amount of JavaScript and that is viewed in lots of different browsers (mobile, tablet, desktop). Naturally we want to log our JavaScript exceptions and their stacktraces, just https://danlimerick.wordpress.com/2014/01/18/how-to-catch-javascript-errors-with-window-onerror-even-on-chrome-and-firefox/ like we log server-side exceptions. It is impossible to test every combination of http://eloquentjavascript.net/1st_edition/chapter5.html device and browser so we rely on logging to find the edge cases we miss in our testing. The way we handle our JavaScript exceptions is to: catch the exception. collect data about the useragent, context etc. Save it to our logs by sending an ajax request with the script error data and the exception information. I can finally log JS Exceptions! We decided to use window.onerror which is a DOM event handler that acts like a global try..catch. This is great for catching unexpected exceptions i.e. the ones that never occur while testing. It is very simple to get started with, you just have to override the handler like this: window.onerror = function handling in javascript (errorMsg, url, lineNumber) { alert('Error: ' + errorMsg + ' Script: ' + url + ' Line: ' + lineNumber); } But It Was Too Good To Be True If you test this on a local server (say IIS or nginx) then it should work fine. But it is not the same as a normal try..catch, so producing a stacktrace with a library like stacktrace.js will probably not work too well. The window.onerror handler does not have the same context and the context varies enormously from browser to browser. Also, if you have minified your files then line number is not very useful. For example: Error: ‘a’ is undefined Script: build.js Line: 3 Variable ‘a' is very hard to find when line 3 has 30000 characters of minified JavaScript. Unfortunately, I do not have a solution for this for all browsers. This will get better over the next few months as a new standard for window.onerror has been agreed upon. It is already implemented for Chrome. The new standard adds two parameters; column number and an error object. Our window.onerror handler now looks like this: window.on
as expected is a good start. Making your programs behave properly when encountering unexpected conditions is where it really gets challenging. ¶ The problematic situations that a program can encounter fall into two categories: Programmer mistakes and genuine problems. If someone forgets to pass a required argument to a function, that is an example of the first kind of problem. On the other hand, if a program asks the user to enter a name and it gets back an empty string, that is something the programmer can not prevent. ¶ In general, one deals with programmer errors by finding and fixing them, and with genuine errors by having the code check for them and perform some suitable action to remedy them (for example, asking for the name again), or at least fail in a well-defined and clean way. ¶ It is important to decide into which of these categories a certain problem falls. For example, consider our old power function:function power(base, exponent) { var result = 1; for (var count = 0; count < exponent; count++) result *= base; return result; } ¶ When some geek tries to call power("Rabbit", 4), that is quite obviously a programmer error, but how about power(9, 0.5)? The function can not handle fractional exponents, but, mathematically speaking, raising a number to the halfth power is perfectly reasonable (Math.pow can handle it). In situations where it is not entirely clear what kind of input a function accepts, it is often a good idea to explicitly state the kind of arguments that are acceptable in a comment. ¶ If a function encounters a problem that it can not solve itself, what should it do? In chapter 4 we wrote the function between:function between(string, start, end) { var startAt = string.indexOf(start) + start.length; var endAt = string.indexOf(end, startAt); return string.slice(startAt, endAt); } ¶ If the given start and end do not occur in the string, indexOf will return -1